1. Field of the Invention
The invention is directed to a differentially steered axle having an access plate to which the steering motor and some of the steering components are mounted.
2. Description of the Prior Art
Differentially steered work vehicles are well known. Differential steering uses changes in wheel speed on the left and right sides of the vehicle to steer. This steering system can be used on tracked and wheeled vehicles. One system that has been used in the prior art is a planetary system having two planetary gear sets. The main drive input from the vehicle transmission drives the sun gear of both planetary gear sets and a steering motor is used to drive the ring gears of both planetary sets. The final drives driving the wheel hubs are coupled to the planetary carriers. Whenever the steering motor increases the speed in one planetary set, the same amount of speed is subtracted from the other planetary set. For example if the speed on one side is increased by three miles per hour, the speed on the other side is decreased three miles per hour. At very slow speeds or when the vehicle is stopped the vehicle can be spin steered. That is the vehicle can be turned on its vertical axis. Typically the steering motor is coupled to the ring gears of the planetary sets by a beveled pinion gear that meshes with the beveled ring gear. An example of this steering system is disclosed in U.S. Pat. No. 4,718,508.
Spur gears have also been used to provide the steering input to the planetary gear sets. If spur gears are used a reverser mechanism is required to provide a rotational change in direction between the planetary sets by the steering motor input. In one example, the main drive input from the vehicle transmission is directed to the planetary carriers of both planetary sets and the steering input is directed to the sun gear of both planetary sets. The steering input is applied to a steering shaft that is parallel to the drive axle. One end of the steering shaft drives a first spur gear which is operatively coupled to the first planetary set. The other end of the steering shaft drives a reverser gear that in turn drives a second spur gear which is operatively coupled to the second planetary gear. The final drives for the wheel hubs are coupled to the ring gear, see U.S. Pat. No. 5,921,335.